BUGS/ISSUES:
  BIC conflict with nlme (S3/S4)

SHORT-TERM:
test!
make relist work/test
documentation:
  - vignette?
  - document methods better

WISHLIST:
analytic derivatives
OR relist

document argument handling

  start must be a named vector or a named list
       [OR?? inherit from parnames(minuslogl)?]
  if start is not a list (i.e. a numeric vector)
  set vecpar TRUE
  convert start to a list

  if missing and default.start is TRUE use formals(minuslogl) 
  [why?]